The present invention generally relates to centrifugal separators and more particularly relates to centrifugal oil filters for engine and vehicle applications.
Current heavy-duty diesel engines put a moderate amount of soot (a form of unburned fuel) into the oil pan. This soot is generated due to the fuel hitting the cold cylinder walls and then being scraped down into the oil sump when the pistons reciprocate in the cylinders. Up until recently, the nitrous oxide emission regulations in the United States and other countries have been high enough that the fuel injection timing could be such that the level of soot generated was not high. In typical applications, the soot level would be under 1% (by weight) of the engine oil at oil drain time. At these low levels, soot in the oil does not cause any significant wear problems.
Recently, there has been a move to significantly lower nitrous oxide emissions which requires much retarded fuel injection timing, which significantly increases the amount of soot being generated. At reasonable oil drain intervals. the soot level may be as high as 4 or 5% with retarded injection timing. When the soot level gets this high, lubrication at critical wear points on the engine becomes so poor that high wear results, significantly decreasing the miles to overhaul and causing high operator expense.
Thus, the engine manufacturer has two choices, suffer very high warranty costs and low miles to overhaul, or significantly lower oil drain intervals to keep high soot levels out of the oil. Neither of these choices is desirable, so there is a current strong need to have a means of getting the soot out of the oil, the subject of this invention.
A problem with removing the soot from oil is that it is very small in sizexe2x80x94around 0.1 to 2.0 micrometers. To remove such small particles from oil using barrier filtration is not feasible due to the large filter size required and the very high probability that the filter will become plugged very rapidly due to trying to filter to such a fine level.
One way that is feasible to remove the soot from the oil is by using a centrifuge, a device that removes the soot from the oil using centrifugal force. This type of device is used to separate blood constituents from blood and has many other applications in typical laboratory applications. The use of a centrifuge for an engine brings a requirement of doing it in a very inexpensive and reliable manner with the centrifuge being easily changed at oil change time. Heretofore, centrifugal filters have not been able to sufficiently remove soot from oil, sufficiently retain the soot, nor reliable enough for use in engine and vehicle applications.
It is an objective of the present invention to provide a reliable and practical apparatus for centrifugal separating soot from engine oil, particularly in vehicle applications.
In accordance with these objectives the present invention is directed toward a novel centrifuge housing for supporting a centrifuge rotor for rotation to separate and filter soot from oil.
One aspect of the present invention relates to reducing the pressure and controlling the flow rate of oil into the centrifuge to control the average residence time for oil in the cartridge. According to this aspect, the centrifuge housing comprises an inlet port connected to the engine to receive oil and an inlet conduit feeding oil from the inlet port into the centrifuge rotor. A restriction plug is interposed along the inlet conduit to provide a restriction controlling the oil feed rate into the centrifuge rotor. An outlet port connected to the engine is adapted to collect filtered oil from the centrifuge rotor and return the oil to the engine.
Another aspect of the present invention relates to equalizing the forces applied to different bearing sets that support the rotation of the centrifuge rotor. According to this aspect, the centrifuge housing comprises a support shaft axially aligned with the predetermined vertical axis that support spaced apart upper and lower bearings. The bearings carry the centrifuge rotor for rotation about the predetermined axis. A spring mechanism supported by the support shaft preloads the upper bearing vertically upward and counteracts the weight of the centrifuge rotor.
Another aspect of the present invention relates to the use of vibration isolators to prevent engine/vehicle induced vibrations and shock loads from being transmitted to the centrifuge rotor during operation. According to this aspect, the centrifuge housing comprises a support body adapted to mount to a vehicle having an internal centrifuge rotor chamber in which the centrifuge rotor is disposed for rotation. A bearing support element carrying bearings supports the centrifuge rotor for rotation about a predetermined axis. At least one vibration isolator is interposed between the bearing support element and support body for reducing transmission of vibrations.
Another aspect of the present invention relates to the novel mechanism for driving the centrifuge rotor. According to this aspect, the centrifuge housing comprises a support housing defining a centrifuge rotor chamber in which the centrifuge rotor is adapted to rotate. The housing includes a support shaft on the predetermined axis having bearings mounted thereon which carry the centrifuge rotor for rotation. An electrical motor supported by the support housing drives the centrifuge rotor directly. The electrical motor includes a stator supported by the outer support body and a motor rotor. The motor rotor comprises a drive sleeve coaxial about the support shaft holding a magnet. The drive sleeve is fixed to the centrifuge rotor such that the centrifuge rotor and centrifuge rotor rotate in unison.
Other objectives and advantages of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.